A method for producing sustainable aviation fuel from straw

Abstract

This invention belongs to the field of aviation fuel technology and provides a method for producing sustainable aviation fuel using straw. First, straw is converted into syngas; then, the syngas and dimethyl ether undergo a catalytic reaction using a primary molecular sieve catalyst. The resulting catalytic product then undergoes a secondary metal catalyst reaction, followed by separation to obtain ethanol; the ethanol is then converted into ethylene; finally, the ethylene is used to produce aviation fuel. The preparation method of the primary molecular sieve catalyst is as follows: a phosphoric acid solution is mixed with deionized water, and a template agent is added (the molar ratio of phosphoric acid to template agent is 1:(0.5-0.55). An aluminum source, a cerium source, and silica sol are added under stirring to obtain a gel; the gel is heated and crystallized; the product is centrifuged, washed until neutral, dried, and calcined; the calcined product is immersed in a zinc nitrate solution, dried, and calcined to obtain a zinc-loaded product; the zinc-loaded product is treated with citric acid solution for dealuminization, followed by calcination to obtain the final product. This invention can significantly improve the ethanol yield in the aviation fuel production process.

Description

Technical Field

[0001] This invention belongs to the field of aviation fuel technology, specifically relating to a method for producing sustainable aviation fuel using straw. Background Technology

[0002] The production of sustainable aviation fuel from straw is mainly achieved through biochemical or thermochemical conversion processes. For example, one existing process for producing aviation fuel from biomass straw consists of four steps: biomass straw is converted into syngas, syngas is converted into ethanol, ethanol is converted into ethylene, and ethylene is converted into aviation fuel.

[0003] The first step involves converting biomass into syngas rich in carbon monoxide, carbon dioxide, and hydrogen through a gasification reaction; this technology has been extensively studied and has mature application examples. The second step is converting the syngas into ethanol, which can be carried out through microbial fermentation or chemical catalysis. The third step is that ethanol can be dehydrated to produce ethylene, a relatively mature chemical process. The fourth step is that ethylene can be further converted into different types of liquid hydrocarbons, including alkanes that can be used as aviation fuel, through polymerization, hydrogenation, and other chemical reactions; this process has wide applications in the petrochemical industry and is relatively mature.

[0004] However, the efficiency, cost, and economic feasibility of the entire process described above still need further optimization. In particular, improving the ethanol yield in the second step, during the syngas-to-ethanol conversion, remains a key research focus. Summary of the Invention

[0005] To address the problems existing in the background art, the present invention provides a method for producing sustainable aviation fuel using straw, which significantly improves the ethanol yield in the aviation fuel production process.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for producing sustainable aviation fuel from straw involves first converting straw into syngas; then reacting the syngas with dimethyl ether using a primary molecular sieve catalyst; the resulting catalytic product is then reacted with a secondary metal catalyst and separated to obtain ethanol; the ethanol is then converted into ethylene; and finally, the ethylene is used to produce aviation fuel. The preparation method of the primary molecular sieve catalyst is as follows:

[0008] A1. Mix 100g of phosphoric acid solution with 290-310g of deionized water, add template agent, the molar ratio of phosphoric acid to template agent is 1:(0.5-0.55), add 170-180g of aluminum source, 0.16-0.2g of cerium source and 50-55g of silica sol while stirring to form a uniform gel;

[0009] A2. Transfer the gel obtained in A1 to a high-pressure reactor and microwave heat it to 160±5℃ for 5.5-6.5h. Centrifuge and wash the product until neutral, dry it at 100-110℃ for 12-13h, and calcine it at 550±10℃ for 3.8-4.2h to remove the template agent and obtain the calcined product.

[0010] A3. Immerse the calcined product obtained in A2 in zinc nitrate solution, dry it, and then calcine it at 450±10℃ for 3-3.5h to obtain the zinc-loaded product.

[0011] A4. The zinc-loaded product obtained in A3 is subjected to dealuminization treatment with citric acid solution to form mesopores (to improve diffusion efficiency), and then activated by calcination to obtain the primary molecular sieve catalyst.

[0012] Furthermore, in A1, the phosphoric acid solution has a wt% ≥ 85%.

[0013] Furthermore, in A1, the template agent is di-n-butylamine; the aluminum source is aluminum isopropoxide; and the cerium source is cerium nitrate.

[0014] Furthermore, in A1, the SiO2 content in the silica sol is 30 wt%.

[0015] Furthermore, in A3, the zinc loading is 2-2.2 wt%.

[0016] Furthermore, in A4, the specific operation of the dealuminization treatment is as follows: the ratio of zinc-loaded product to 0.1 mol / L citric acid solution is 1 g: (16-20) mL, constant temperature water bath at 85±5℃, stirring at 180-220 r / min for 2-2.5 h.

[0017] Furthermore, in A4, the specific operation of roasting and activation is as follows: nitrogen gas is pre-purged into the muffle furnace (flow rate 45-50 mL / min) until the oxygen content is <0.1%, the temperature is first increased to 300±5℃ at 2-3℃ / min and held for 1h, then the temperature is increased to 480±5℃ at 1-1.5℃ / min and held for 3h, and then cooled with the furnace.

[0018] Furthermore, the secondary metal catalyst is a bimetallic catalyst.

[0019] Furthermore, the secondary metal catalyst is a Co-Cu catalyst.

[0020] This application has the following beneficial effects:

[0021] In the preparation of the primary molecular sieve catalyst of this invention, cerium nitrate, a cerium source, is introduced based on a molar ratio of phosphoric acid to template agent of 1:(0.5-0.55). On one hand, Ce acts as a "structural repair agent," and the residual carbon formed by the high-temperature carbonization of excess di-n-butylamine is transformed into a mesoporous pore-forming agent in the presence of cerium nitrate, etching mesopores on the micropore walls, increasing the proportion of mesoporous channels, and thus improving the syngas diffusion rate; furthermore, Ce… 4+ Oxygen vacancy migration compensates for skeletal distortion caused by excessive template agent, repairs lattice defects, and counteracts the negative effects of excessive template agent.

[0022] On the other hand, Ce acts as an "acid site regulator." CeO2 nanoparticles formed through high-temperature conversion preferentially anchor to strong L acid sites, reducing side reactions, inhibiting ethanol dehydration, and retaining medium-strong Brønsted acid sites, thus promoting CO insertion to form CH3CO*. Furthermore, CeO2 reacts with Zn... 2+ A Ce-O-Zn heterostructure is formed, which optimizes electron transport in Zn. 2+ The upward shift of the d-band center enhances the adsorption of *CH3CHO, lowers the H2 dissociation energy barrier, and increases the hydrogenation rate of acetaldehyde.

[0023] In summary, Ce, through its dual functions as a "structural repair agent" and an "acid site regulator," transforms excess template agent from a "defect source" into a "mesoporosis generation aid," synergistically improving diffusion efficiency and hydrogenation rate, thereby synergistically increasing ethanol yield. Attached Figure Description

[0024] Figure 1 This is a trend chart comparing the ethanol yields of Examples 1-3 and Comparative Examples 1-3 in the experimental examples of this invention. Detailed Implementation

[0025] The present application will be further described in detail below with reference to the embodiments.

[0026] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0027] Example 1: (a) Preparation of primary molecular sieve catalyst, the preparation method is as follows:

[0028] A1. Mix 100g of phosphoric acid solution (wt% 85%) with 300g of deionized water, add the template agent di-n-butylamine, the molar ratio of phosphoric acid to di-n-butylamine is 1:0.52, stir at 200r / min, add 175g of aluminum source aluminum isopropoxide, 0.18g of cerium source cerium nitrate and 52g of silica sol (SiO2 content is 30wt%) to form a uniform gel.

[0029] A2. The gel obtained in A1 was transferred to a high-pressure reactor and microwaved to about 160°C for 6 hours to crystallize. The product was centrifuged and washed until neutral, dried at 105°C for 12.5 hours, and calcined at about 550°C for 4 hours to remove the template agent, thus obtaining the calcined product.

[0030] A3. The calcined product obtained in A2 was immersed in zinc nitrate solution, dried, and then calcined at 450℃ for 3.2h to obtain a zinc-loaded product; the zinc loading was 2.1wt%.

[0031] A4. The zinc-loaded product obtained in A3 was subjected to dealumination treatment with citric acid solution. The specific operation was as follows: the ratio of zinc-loaded product to 0.1 mol / L citric acid solution was 1 g: 18 mL. The mixture was placed in a constant temperature water bath at approximately 85°C and stirred at 200 r / min for 2.2 h to form mesopores (improving diffusion efficiency). The product was then re-calcined and activated. The specific operation was as follows: nitrogen gas was pre-purged into the muffle furnace (flow rate 50 mL / min) until the oxygen content was <0.1%. The temperature was first increased to approximately 300°C at a rate of 2°C / min and held for 1 h. Then, the temperature was increased to approximately 480°C at a rate of 1°C / min and held for 3 h. The product was then cooled with the furnace to obtain the primary molecular sieve catalyst.

[0032] (II) Preparation of Co-Cu catalyst, the preparation method is as follows:

[0033] B1. Dissolve 10g of Na2C2O4 in 350mL of deionized water, add 4.4g of copper nitrate trihydrate, stir until a deep blue transparent solution is obtained, seal and let stand at low temperature for 12h until crystallization is complete, filter, wash with anhydrous ethanol, and dry in an oven at 50℃ for 6h to obtain crystals.

[0034] B2. Dissolve 3.02g of cobalt nitrate hexahydrate, 12.69g of zinc nitrate hexahydrate, and 8.00g of aluminum nitrate nonahydrate in 200ml of deionized water to obtain mixed salt solution a. Dissolve 3.63g of NaNO3 and 5.38g of NaOH in 200ml of deionized water to obtain mixed salt solution b. Mixed salt solution a and mixed salt solution b are vigorously stirred in a three-necked flask to obtain a pink slurry precipitate. After vigorous stirring for 5 minutes, the temperature is raised to 100℃ and slowly stirred for 12 hours to crystallize. After filtration and washing with deionized water, the precipitate is washed with ethanol and then dried in a vacuum oven at 60℃ overnight. The precipitate is then ground to obtain a powder.

[0035] B3. Take the crystals obtained in B1 and the powder obtained in B2, mix them at a Co / Cu molar ratio of 1.5:1 to prepare a 0.015 mol / L mixed aqueous solution, add hydrotalcite powder, the amount of hydrotalcite powder added is 0.5% of the mixed aqueous solution, stir at room temperature for 12 h, filter and wash, dry under vacuum at 60℃ for 12 h, grind, and the Co-Cu catalyst is obtained.

[0036] (iii) A method for producing sustainable aviation fuel using straw includes the following steps:

[0037] First, syngas and dimethyl ether are fed into a fixed-bed reactor, passing through a primary molecular sieve catalyst, and undergoing a catalytic reaction at 220°C and 6 MPa to obtain the primary product; the volume ratio of CO to H2 in the syngas is 1:1. The primary product is then passed to a Co-Cu catalyst, where it undergoes a catalytic reaction at 260°C and 12 MPa to obtain the secondary product. The fixed-bed reactor containing the primary molecular sieve catalyst and the fixed-bed reactor containing the Co-Cu catalyst are connected in series. The secondary product is then separated to obtain ethanol.

[0038] Example 2: The difference between this example and Example 1 is that the primary molecular sieve catalyst is prepared, and the preparation method is as follows:

[0039] A1. Mix 100g of phosphoric acid solution (wt% 85%) with 290g of deionized water, add the template agent di-n-butylamine, the molar ratio of phosphoric acid to di-n-butylamine is 1:0.5, add 170g of aluminum source aluminum isopropoxide, 0.16g of cerium source cerium nitrate and 50g of silica sol (SiO2 content is 30wt%) while stirring to form a uniform gel.

[0040] A2. Transfer the gel obtained in A1 to a high-pressure reactor and microwave it to about 160°C for 6 hours to crystallize. Centrifuge and wash the product until it is neutral, dry it at 105°C for 12 hours, and calcine it at about 550°C for 4 hours to remove the template agent and obtain the calcined product.

[0041] A3. The calcined product obtained in A2 was immersed in zinc nitrate solution, dried, and then calcined at about 450°C for 3.2 hours to obtain the zinc-loaded product; the zinc loading was 2 wt%.

[0042] A4. The zinc-loaded product obtained in A3 was subjected to dealumination treatment with citric acid solution. The specific operation was as follows: the ratio of zinc-loaded product to 0.1 mol / L citric acid solution was 1 g: 16 mL. The mixture was placed in a constant temperature water bath at approximately 85°C and stirred at 180 r / min for 2.5 h to form mesopores (improving diffusion efficiency). The product was then re-calcined and activated. The specific operation was as follows: nitrogen gas was pre-purged into the muffle furnace (flow rate 50 mL / min) until the oxygen content was <0.1%. The temperature was first increased to approximately 300°C at a rate of 2°C / min and held for 1 h. Then, the temperature was increased to approximately 480°C at a rate of 1°C / min and held for 3 h. The product was then cooled with the furnace to obtain the primary molecular sieve catalyst.

[0043] Example 3: The difference between this example and Example 1 is that the primary molecular sieve catalyst is prepared, and the preparation method is as follows:

[0044] A1. Mix 100g of phosphoric acid solution (wt% 85%) with 310g of deionized water, add the template agent di-n-butylamine, the molar ratio of phosphoric acid to di-n-butylamine is 1:0.55, add 180g of aluminum source aluminum isopropoxide, 0.2g of cerium source cerium nitrate and 55g of silica sol (SiO2 content is 30wt%) while stirring to form a uniform gel.

[0045] A2. Transfer the gel obtained in A1 to a high-pressure reactor, microwave it to about 160°C, and crystallize it for 6 hours. Centrifuge and wash the product until it is neutral, dry it at 110°C for 12 hours, and calcine it at about 550°C for 4 hours to remove the template agent and obtain the calcined product.

[0046] A3. The calcined product obtained in A2 was immersed in zinc nitrate solution, dried, and then calcined at about 450°C for 3.2 h to obtain the zinc-loaded product; the zinc loading was 2.2 wt%.

[0047] A4. The zinc-loaded product obtained in A3 was subjected to dealumination treatment with citric acid solution. The specific operation was as follows: the ratio of zinc-loaded product to 0.1 mol / L citric acid solution was 1 g: 20 mL. The mixture was placed in a constant temperature water bath at approximately 85°C and stirred at 220 r / min for 2 h to form mesopores (improving diffusion efficiency). The product was then re-calcined and activated. The specific operation was as follows: nitrogen gas was pre-purged into the muffle furnace (flow rate 50 mL / min) until the oxygen content was <0.1%. The temperature was first increased to approximately 300°C at a rate of 2°C / min and held for 1 h. Then, the temperature was increased to approximately 480°C at a rate of 1°C / min and held for 3 h. The product was then cooled with the furnace to obtain the primary molecular sieve catalyst.

[0048] Comparative Example 1: The difference between this comparative example and Example 1 is that the molar ratio of phosphoric acid and template agent di-n-butylamine is 1:0.4, and cerium nitrate is omitted.

[0049] Specifically, the preparation method for the primary molecular sieve catalyst is as follows:

[0050] A1. Mix 100g of phosphoric acid solution (wt% 85%) with 300g of deionized water, add the template agent di-n-butylamine, the molar ratio of phosphoric acid to di-n-butylamine is 1:0.4, stir at 200r / min, add 175g of aluminum source aluminum isopropoxide and 52g of silica sol (SiO2 content is 30wt%) to form a uniform gel.

[0051] A2. The gel obtained in A1 was transferred to a high-pressure reactor and microwaved to about 160°C for 6 hours to crystallize. The product was centrifuged and washed until neutral, dried at 105°C for 12.5 hours, and calcined at about 550°C for 4 hours to remove the template agent, thus obtaining the calcined product.

[0052] A3. The calcined product obtained in A2 was immersed in zinc nitrate solution, dried, and then calcined at 450℃ for 3.2h to obtain a zinc-loaded product; the zinc loading was 2.1wt%.

[0053] A4. The zinc-loaded product obtained in A3 was subjected to dealumination treatment with citric acid solution. The specific operation was as follows: the ratio of zinc-loaded product to 0.1 mol / L citric acid solution was 1 g: 18 mL. The mixture was placed in a constant temperature water bath at approximately 85°C and stirred at 200 r / min for 2.2 h to form mesopores (improving diffusion efficiency). The product was then re-calcined and activated. The specific operation was as follows: nitrogen gas was pre-purged into the muffle furnace (flow rate 50 mL / min) until the oxygen content was <0.1%. The temperature was first increased to approximately 300°C at a rate of 2°C / min and held for 1 h. Then, the temperature was increased to approximately 480°C at a rate of 1°C / min and held for 3 h. The product was then cooled with the furnace to obtain the primary molecular sieve catalyst.

[0054] Comparative Example 2: The difference between this comparative example and Example 1 is that cerium nitrate is removed.

[0055] Comparative Example 3: The difference between this comparative example and Example 1 is that the molar ratio of phosphoric acid and the template agent di-n-butylamine is 1:0.4.

[0056] Experimental Examples: Test Subjects: Examples 1-3 and Comparative Examples 1-3. Test Item: Ethanol yield (based on primary molecular sieve catalyst). Test Results: See Table 1.

[0057] Table 1. Experimental Results Data for the Experimental Case

[0058] Ethanol yield / g / kgcat / h Example 1 392.8 Example 2 387.7 Example 3 384.4 Comparative Example 1 358.7 Comparative Example 2 334.1 Comparative Example 3 372.5

[0059] Results Analysis: Analysis of Examples 1-3, combined with data from Table 1 and... Figure 1 As can be seen, in the process of producing ethanol from syngas in this invention (Examples 1-3), the ethanol yield is as high as 384.4 g / kgcat / h (based on primary molecular sieve catalyst).

[0060] Analyze Example 1 and Comparative Examples 1-3 and combine the data in Table 1 and Figure 1 Specifically, comparing Comparative Example 1 and Comparative Example 2, it can be seen that compared to Comparative Example 1 where the molar ratio of phosphoric acid to the template agent di-n-butylamine in the preparation of the primary molecular sieve catalyst was 1:0.4, the molar ratio in Comparative Example 2 was 1:0.52. As a result, the ethanol yield decreased from 358.7 g / kgcat / h to 334.1 g / kgcat / h. This indicates that increasing the amount of the template agent di-n-butylamine to an excessive level will lead to a decrease in ethanol yield instead of an increase.

[0061] This is mainly because the molar ratio of phosphoric acid to the template agent decreased from 1:0.4 to 1:0.52. On the one hand, the excess of the template agent di-n-butylamine, after high-temperature calcination, resulted in residual amine carbides that blocked the micropores (pore size <1nm), hindering the diffusion of syngas to the active sites and reducing the reactant contact efficiency. On the other hand, the excess template agent interfered with the ordered arrangement of the framework, causing local lattice distortion, leading to uneven distribution of acidic sites and reducing CO activation sites; it also caused Zn... 2+ Abnormalities in the loading sites weaken its ability to hydrogenate aldehyde intermediates, resulting in reduced ethanol selectivity.

[0062] Comparing Comparative Examples 1 and 3, it can be seen that, compared to Comparative Example 1, the addition of cerium nitrate in step A1 of Comparative Example 3 resulted in an increase in ethanol yield from 358.7 g / kgcat / h to 372.5 g / kgcat / h. This indicates that, based on a molar ratio of phosphoric acid to the template agent di-n-butylamine of 1:0.4 in the preparation of the primary molecular sieve catalyst, the addition of cerium nitrate in step A1 can improve the ethanol yield.

[0063] This is mainly because, with the addition of cerium nitrate in the A1 step, CeO2 preferentially anchors at strong Lewis acid (L acid) sites in the molecular sieve framework, forming a Ce-O-Al / Si coordination structure. This inhibits excessive dehydration and effectively blocks the ethanol→ethylene dehydration pathway. The retained medium-strong Brønsted acid (B acid) sites promote the formation of key intermediates, enhance CO insertion ability, accelerate CH3CO* (acetyl) formation, and improve the selectivity of C2 oxygen-containing compounds. CeO2 and Zn 2+ The formation of a Ce-O-Zn heterointerface alters the electron transport pathway, enabling Zn... 2+ Exhibiting an electron-deficient state (Znδ) + This enhances the adsorption energy of acetaldehyde (*CH3CHO), lowers the hydrogenation energy barrier, and increases the ethanol production rate.

[0064] In comparison with Example 1, it can be seen that the molar ratio of phosphoric acid and template agent decreased from 1:0.4 to 1:0.52; and the addition of cerium nitrate in step A1 resulted in a synergistic effect between the two, which synergistically improved the ethanol yield.

[0065] This is mainly because Ce, through its dual function as a "structural repair agent" and an "acid site regulator," transforms excess template agent from a "defect source" into a "mesoporosis generation aid," synergistically improving diffusion efficiency and hydrogenation rate, thereby synergistically increasing ethanol yield.

[0066] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0067] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for producing sustainable aviation fuel from straw, comprising: first, converting straw into syngas; then, reacting the syngas with dimethyl ether through a primary molecular sieve catalyst; further reacting the resulting catalytic product through a secondary metal catalyst, separating the reacted products to obtain ethanol; then, converting the ethanol into ethylene; and finally, converting the ethylene into aviation fuel; characterized in that... The preparation method of the primary molecular sieve catalyst is as follows: A1. Mix 100g of phosphoric acid solution with 290-310g of deionized water, add template agent, the molar ratio of phosphoric acid to template agent is 1:(0.5-0.55), add 170-180g of aluminum source, 0.16-0.2g of cerium source and 50-55g of silica sol while stirring to form a uniform gel; A2. Heat the gel obtained in A1 to 160±5℃ and crystallize for 5.5-6.5h; centrifuge and wash the product until neutral, dry at 100-110℃ for 12-13h, and calcine at 550±10℃ for 3.8-4.2h to obtain the calcined product. A3. Immerse the calcined product obtained in A2 in zinc nitrate solution, dry it, and then calcine it at 450±10℃ for 3-3.5h to obtain the zinc-loaded product. A4. The zinc-loaded product obtained in A3 is subjected to dealuminization treatment with citric acid solution, and then activated by calcination to obtain the primary molecular sieve catalyst.

2. The method of producing sustainable aviation fuel from straw according to claim 1, wherein, In A1, the phosphoric acid solution has a wt% ≥ 85%.

3. The method of producing sustainable aviation fuel from straw according to claim 1, wherein, In A1, the template agent is di-n-butylamine; the aluminum source is aluminum isopropoxide; and the cerium source is cerium nitrate.

4. The method of producing sustainable aviation fuel from straw according to claim 1, wherein, In A1, the SiO2 content in the silica sol is 30wt%.

5. The method of producing sustainable aviation fuel from straw according to claim 1, wherein, In A3, the zinc loading is 2-2.2 wt%.

6. The method of producing sustainable aviation fuel from straw according to claim 1, wherein, In A4, the specific operation of the dealuminization treatment is as follows: the ratio of zinc-loaded product to 0.1 mol / L citric acid solution is 1 g: (16-20) mL, constant temperature water bath at 85±5℃, stirring at 180-220 r / min for 2-2.5 h.

7. The method of producing sustainable aviation fuel from straw according to claim 1, wherein, In A4, the specific operation of roasting and activation is as follows: nitrogen gas is pre-purged into the muffle furnace until the oxygen content is <0.1%. The temperature is first increased to 300±5℃ at 2-3℃ / min and held for 1 hour. Then the temperature is increased to 480±5℃ at 1-1.5℃ / min and held for 3 hours. The furnace is then cooled.

8. The method of producing sustainable aviation fuel from straw according to claim 1, wherein, The secondary metal catalyst is a bimetallic catalyst.

9. The method of producing sustainable aviation fuel from straw according to claim 8, wherein, The secondary metal catalyst is a Co-Cu catalyst.

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